A man holds on to a prison bar inside of a jail cell. (Photo by Daniel Berehulak/Getty Images)

A man holds on to a prison bar inside of a jail cell. (Photo by Daniel Berehulak/Getty Images)

UPDATED 08/24/11 6:06 p.m.

CHICAGO (CBS) — Prosecutors and police on Wednesday announced charges against Chicago gang members in a unique human trafficking investigation.

As CBS 2’s Mike Puccinelli reports, for the first time in the state, law enforcement officials used wiretaps approved by a judge to gather evidence of human trafficking.

The Cook County State’s Attorney’s office said that “Operation Little Girl Lost” utilized the new Illinois Safe Children’s Act to arrest and charge gang members for forcing young women and girls into prostitution.

Four people appeared in bond court Wednesday in connection with the sex trafficking operation. Allen Sahura, Jaymes Hart, Travis Creekmore and Jerrell Creekmore were all charged with involuntary servitude of a minor and human trafficking. They were among nine people arrested, following an 18-month investigation.

The eight men and one woman charged in the case have been accused of forcing children – some as young as 12 – to have sex for money. Police said that, in some cases, the crimes were actually heard by investigators listening into wiretapped phone conversations.

“In a few instances we actually have recorded cases of girls being beaten and abused and stuff like that, which was difficult to listen to,” said Cook County Sheriff’s Police Vice Unit Commander Mike Anton.

Operation Little Girl Lost marks the first time in the nation that a state has used wiretaps to target the crime of human trafficking.

Cook County State’s Attorney Anita Alvarez said it’s a tool whose time had come.

“We’ve always had the opportunity and the ability to go up on a wire for people who were selling drugs, but not for people who were selling children, which I find quite offensive, certainly as a mother of four children,” Alvarez said.

Prosecutors said that dozens of minor girls were targeted in a trafficking ring that had up to 100 victims who were sexually abused in hotels and homes around the city.

A 13-year-old victim told investigators she’d been selling her body since she was 11 years old. At one point, prosecutors said, she was sold from one pimp to another one for $100.

“It’s cases like this that are not easy for investigators, because it pulls at your heartstrings when young girls are exploited in such a fashion,” Chicago Police Supt. Garry McCarthy said.

Two women who were in court on Wednesday in support of Jaymes Hart didn’t want to go on camera, but said they know nothing of alleged criminal activity.

All nine defendants face up to 30 years in prison if convicted. Authorities are treating all of the girls and young women who had sex for money – including those older than 18 – as victims, in part because of the brutal tactics of their pimps.